gitea/modules/markup/markdown/markdown.go

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// Copyright 2014 The Gogs Authors. All rights reserved.
// Copyright 2018 The Gitea Authors. All rights reserved.
// SPDX-License-Identifier: MIT
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package markdown
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import (
"fmt"
"html/template"
"io"
"strings"
"sync"
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"code.gitea.io/gitea/modules/log"
"code.gitea.io/gitea/modules/markup"
"code.gitea.io/gitea/modules/markup/common"
"code.gitea.io/gitea/modules/markup/markdown/math"
"code.gitea.io/gitea/modules/setting"
giteautil "code.gitea.io/gitea/modules/util"
chromahtml "github.com/alecthomas/chroma/v2/formatters/html"
"github.com/yuin/goldmark"
highlighting "github.com/yuin/goldmark-highlighting/v2"
meta "github.com/yuin/goldmark-meta"
"github.com/yuin/goldmark/extension"
"github.com/yuin/goldmark/parser"
"github.com/yuin/goldmark/renderer"
"github.com/yuin/goldmark/renderer/html"
"github.com/yuin/goldmark/util"
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)
var (
specMarkdown goldmark.Markdown
specMarkdownOnce sync.Once
)
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var (
renderContextKey = parser.NewContextKey()
renderConfigKey = parser.NewContextKey()
)
type limitWriter struct {
w io.Writer
sum int64
limit int64
}
// Write implements the standard Write interface:
func (l *limitWriter) Write(data []byte) (int, error) {
leftToWrite := l.limit - l.sum
if leftToWrite < int64(len(data)) {
n, err := l.w.Write(data[:leftToWrite])
l.sum += int64(n)
if err != nil {
return n, err
}
return n, fmt.Errorf("rendered content too large - truncating render")
}
n, err := l.w.Write(data)
l.sum += int64(n)
return n, err
}
// newParserContext creates a parser.Context with the render context set
func newParserContext(ctx *markup.RenderContext) parser.Context {
pc := parser.NewContext(parser.WithIDs(newPrefixedIDs()))
pc.Set(renderContextKey, ctx)
return pc
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}
// SpecializedMarkdown sets up the Gitea specific markdown extensions
func SpecializedMarkdown() goldmark.Markdown {
specMarkdownOnce.Do(func() {
specMarkdown = goldmark.New(
goldmark.WithExtensions(
extension.NewTable(
extension.WithTableCellAlignMethod(extension.TableCellAlignAttribute)),
extension.Strikethrough,
extension.TaskList,
extension.DefinitionList,
common.FootnoteExtension,
highlighting.NewHighlighting(
highlighting.WithFormatOptions(
chromahtml.WithClasses(true),
chromahtml.PreventSurroundingPre(true),
),
highlighting.WithWrapperRenderer(func(w util.BufWriter, c highlighting.CodeBlockContext, entering bool) {
if entering {
language, _ := c.Language()
if language == nil {
language = []byte("text")
}
languageStr := string(language)
preClasses := []string{"code-block"}
if languageStr == "mermaid" || languageStr == "math" {
preClasses = append(preClasses, "is-loading")
}
_, err := w.WriteString(`<pre class="` + strings.Join(preClasses, " ") + `">`)
if err != nil {
return
}
// include language-x class as part of commonmark spec
// the "display" class is used by "js/markup/math.js" to render the code element as a block
_, err = w.WriteString(`<code class="chroma language-` + string(language) + ` display">`)
if err != nil {
return
}
} else {
_, err := w.WriteString("</code></pre>")
if err != nil {
return
}
}
}),
),
math.NewExtension(
math.Enabled(setting.Markdown.EnableMath),
),
meta.Meta,
),
goldmark.WithParserOptions(
parser.WithAttribute(),
parser.WithAutoHeadingID(),
parser.WithASTTransformers(
util.Prioritized(NewASTTransformer(), 10000),
),
),
goldmark.WithRendererOptions(
html.WithUnsafe(),
),
)
// Override the original Tasklist renderer!
specMarkdown.Renderer().AddOptions(
renderer.WithNodeRenderers(
util.Prioritized(NewHTMLRenderer(), 10),
),
)
})
return specMarkdown
}
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// actualRender renders Markdown to HTML without handling special links.
func actualRender(ctx *markup.RenderContext, input io.Reader, output io.Writer) error {
converter := SpecializedMarkdown()
lw := &limitWriter{
w: output,
limit: setting.UI.MaxDisplayFileSize * 3,
}
// FIXME: should we include a timeout to abort the renderer if it takes too long?
defer func() {
err := recover()
if err == nil {
return
}
log.Warn("Unable to render markdown due to panic in goldmark: %v", err)
if log.IsDebug() {
log.Debug("Panic in markdown: %v\n%s", err, log.Stack(2))
}
}()
// FIXME: Don't read all to memory, but goldmark doesn't support
pc := newParserContext(ctx)
buf, err := io.ReadAll(input)
if err != nil {
log.Error("Unable to ReadAll: %v", err)
return err
}
buf = giteautil.NormalizeEOL(buf)
// Preserve original length.
bufWithMetadataLength := len(buf)
rc := &RenderConfig{
Meta: renderMetaModeFromString(string(ctx.RenderMetaAs)),
Icon: "table",
Lang: "",
}
buf, _ = ExtractMetadataBytes(buf, rc)
metaLength := bufWithMetadataLength - len(buf)
if metaLength < 0 {
metaLength = 0
}
rc.metaLength = metaLength
pc.Set(renderConfigKey, rc)
if err := converter.Convert(buf, lw, parser.WithContext(pc)); err != nil {
log.Error("Unable to render: %v", err)
return err
}
return nil
}
// Note: The output of this method must get sanitized.
func render(ctx *markup.RenderContext, input io.Reader, output io.Writer) error {
defer func() {
err := recover()
if err == nil {
return
}
log.Warn("Unable to render markdown due to panic in goldmark - will return raw bytes")
if log.IsDebug() {
log.Debug("Panic in markdown: %v\n%s", err, log.Stack(2))
}
_, err = io.Copy(output, input)
if err != nil {
log.Error("io.Copy failed: %v", err)
}
}()
return actualRender(ctx, input, output)
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}
// MarkupName describes markup's name
var MarkupName = "markdown"
func init() {
markup.RegisterRenderer(Renderer{})
}
// Renderer implements markup.Renderer
type Renderer struct{}
var _ markup.PostProcessRenderer = (*Renderer)(nil)
// Name implements markup.Renderer
func (Renderer) Name() string {
return MarkupName
}
// NeedPostProcess implements markup.PostProcessRenderer
func (Renderer) NeedPostProcess() bool { return true }
// Extensions implements markup.Renderer
func (Renderer) Extensions() []string {
return setting.Markdown.FileExtensions
}
// SanitizerRules implements markup.Renderer
func (Renderer) SanitizerRules() []setting.MarkupSanitizerRule {
return []setting.MarkupSanitizerRule{}
}
// Render implements markup.Renderer
func (Renderer) Render(ctx *markup.RenderContext, input io.Reader, output io.Writer) error {
return render(ctx, input, output)
}
// Render renders Markdown to HTML with all specific handling stuff.
func Render(ctx *markup.RenderContext, input io.Reader, output io.Writer) error {
if ctx.Type == "" {
ctx.Type = MarkupName
}
return markup.Render(ctx, input, output)
}
// RenderString renders Markdown string to HTML with all specific handling stuff and return string
func RenderString(ctx *markup.RenderContext, content string) (template.HTML, error) {
var buf strings.Builder
if err := Render(ctx, strings.NewReader(content), &buf); err != nil {
return "", err
}
return template.HTML(buf.String()), nil
}
// RenderRaw renders Markdown to HTML without handling special links.
func RenderRaw(ctx *markup.RenderContext, input io.Reader, output io.Writer) error {
rd, wr := io.Pipe()
defer func() {
_ = rd.Close()
_ = wr.Close()
}()
go func() {
if err := render(ctx, input, wr); err != nil {
_ = wr.CloseWithError(err)
return
}
_ = wr.Close()
}()
return markup.SanitizeReader(rd, "", output)
}
// RenderRawString renders Markdown to HTML without handling special links and return string
func RenderRawString(ctx *markup.RenderContext, content string) (string, error) {
var buf strings.Builder
if err := RenderRaw(ctx, strings.NewReader(content), &buf); err != nil {
return "", err
}
return buf.String(), nil
}